1. Field of the Invention
The present invention relates to a print control apparatus, a control method thereof, and a storage medium, and particularly to a print control apparatus capable of printing both surfaces of roll paper, a control method thereof, and a storage medium.
2. Description of the Related Art
Printing apparatuses have conventionally used various methods of double-sided printing on roll paper.
For example, there are a method of printing a front surface and a back surface without cutting roll paper into predetermined units and a method of printing a front surface and a back surface after cutting roll paper into predetermined units. When roll paper is cut into predetermined units before printing and handled like cut paper, printing can be done like printing on normal cut paper. On the other hand, when printing a small part of roll paper, for example, performing double-sided printing on roll paper corresponding to only one A4-size sheet, front surface printing is performed on the uncut roll paper. The roll paper is cut after the front surface printing, and the back surface of the roll paper (to be referred to as printed roll paper hereinafter) that has undergone the front surface printing is then printed. When performing front surface printing on roll paper, cutting the roll paper, and then performing back surface printing on the cut paper, as described above, the shape of the print medium changes between the front surface printing and the back surface printing.
Focusing on the difference in the state of the print medium between front surface printing and back surface printing, an extra margin is added to the rear end of the paper with the front surface image printed, and the roll paper is cut in this state. When inverting the cut print medium and refeeding the back surface, the print medium is conveyed such that the extra margin comes to the front end. There has been proposed such an inkjet printing apparatus (for example, Japanese Patent Laid-Open No. 2007-144960).
In Japanese Patent Laid-Open No. 2007-144960, however, the difference in the shape of the print medium when double-sided printing the printed roll paper is not taken into consideration.
When double-sided printing is executed for roll paper, which undergoes front surface printing as roll paper and undergoes back surface printing in a state close to cut paper, unevenness or a problem in printing may occur, as will be described later.
For example, when roll paper used in a large-scale printing apparatus is wide or long, the weight increases. When the roll paper is wound on a print medium paper tube, the weight of the paper tube is also included. For this reason, some printing apparatuses limit the maximum weight of roll paper to, for example, 40 kg. It is therefore necessary to increase the driving force to convey the roll paper.
Since even relatively light-weight roll paper that is narrow and short is conveyed by the same driving force, a back tension is added to the roll paper to apply a torque in a direction opposite to the conveyance direction. Hence, a force larger than the back tension by its own weight is applied.
On the other hand, in cut paper printing, a print medium is cut into a standard size or the like in advance. Some printing apparatuses limit the maximum length to, for example, 1.6 m. Hence, the cut paper weighs only several hundred grams and is much lighter than roll paper. For this reason, the back tension applied to a print medium at the time of conveyance largely changes between roll paper and cut paper even if the surface quality of the print medium is the same.
Since the roll paper receives a larger force of its own weight and the above-described back tension with respect to the same rotation amount of the conveyance rollers, a large amount of paper slip occurs, and the actual print medium conveyance amount decreases.
When printing cut printed roll paper as roll paper, the back tension applied to the print medium at the time of driving is smaller than that for roll paper. For this reason, when a normal conveyance amount is used, the print medium is conveyed too much, resulting in, for example, stripes in the printed image.
In addition, the paper floating amount also changes between roll paper wound into a roll and flat cut paper. When double-sided printing cut printed roll paper as roll paper, sucking may be too much, the print medium may stick to the platen, and conveyance may become impossible. Conversely, sucking may be too weak, resulting in paper floating.
In an inkjet printing apparatus, the head height changes not to make the ink discharge surface of the printhead contact the print medium at the time of paper floating. However, if cut printed roll paper is printed in the setting of roll paper, an appropriate height cannot be obtained.